Prevent Duplication when sharing

Numbers doesn’t have a built-in way to fully prevent someone from duplicating a shared file. You could try using iCloud’s file sharing options, which let you share a file with restricted permissions. Apple has an official guide on how to do this: Use iCloud to share and collaborate on files and folders - Apple Support

Still, even with these restrictions, there’s no way to completely prevent someone from manually capturing the data, such as by taking screenshots.